1. Field of the Invention.
This invention relates generally to methods and apparatus for covering liquids in a surface depression, and more particularly, but not by way of limitation, to methods and apparatus for covering drilling mud returns in a drilling mud pit.
2. Description of the Prior Art.
Drilling mud returns from a well have generally been stored in surface depressions of one type or another, with most of such depressions having been manmade. An older method of disposing of such drilling mud returns involves digging long, deep trenches with a backhoe or similar device, pumping the returns into the trenches, and pushing soil on top of the drilling mud returns within the trenches with a bulldozer or by some other means. The primary difficulty encountered with this method is that drilling mud tends to flow out from underneath the weight of soil placed on top of the mud by flowing toward the ends of the trench. To effectively cover all of the drilling mud, then, the trench must frequently be lengthened to an excessive extent, thereby wasting time, manhours and equipment.
A newer method of disposing of the drilling mud returns involves placing the returns from various wells into a centralized disposal pit. Such pits are not infrequently a quarter of a mile in length, while being several hundred feet wide and from nine to thirty feet in depth. Disposal of the returns, as before, is generally accomplished by using a bulldozer to push soil into the pit on top of the returns. The weight of soil so placed, however, is generally too great and too localized, such that the same problem of the returns flowing out from underneath the soil is encountered.
Other soil displacing devices are known, however, which attempt to distribute the soil more evenly as it is displaced, such as that disclosed in U.S. Pat. No. 3,804,178 to West. A frame having an upright, horizontally elongated blade attached thereto is located at the forward end of a tractor. A horizontally disposed and rotatable vaned disk composed of a horizontally disposed plate and a plurality of vertically positioned vanes is located at the trailing end of the blade for throwing soil directed by the blade toward the disk. The disk is rotated by an auxiliary engine to throw the soil directed by the blade toward the disk.
The apparatus is disclosed as being tiltable laterally on an axis parallel to the path of travel of the tractor and is vertically movable, but as shown by its placement forward of the vehicle and the provision of the auxiliary engine, is not disclosed as advantageously attachable to the power take-off of a conventional farm tractor.
Further, the size of the blade provided makes adjustments for varying soil conditions impracticable over a small area. Such adjustments may be desirable, for instance, where soils of vastly different densities are presented within such a small area. The distribution of such soils over the surface of drilling mud returns can lead to the sort of uneven loading encountered with earlier methods, and thus to holes and gaps in the layer of soil covering the liquid where the liquid has flowed out from underneath the layer.